Source: Proceedings of the National Academy of Sciences of the United States of America
Published online before print July 31, 2006, 10.1073/pnas.0604815103
PNAS | August 8, 2006 | vol. 103 | no. 32 | 11856-11861

A viral resistance gene from common bean functions across plant families and is up-regulated in a non-virus-specific manner
Young-Su Seo, Maria R. Rojas, Jung-Youn Lee, Sang-Won Lee, Jong-Seong Jeon, Pamela Ronald, William J. Lucas, and Robert L. Gilbertson

ABSTRACT

Genes involved in a viral resistance response in common bean (Phaseolus vulgaris cv. Othello) were identified by inoculating a geminivirus reporter (Bean dwarf mosaic virus expressing the green fluorescent protein), extracting RNA from tissue undergoing the defense response, and amplifying sequences with degenerate R gene primers. One such gene (a TIR-NBS-LRR gene, RT4-4) was selected for functional analysis in which transgenic Nicotiana benthamiana were generated and screened for resistance to a range of viruses. This analysis revealed that RT4-4 did not confer resistance to the reporter geminivirus; however, it did activate a resistance-related response (systemic necrosis) to seven strains of Cucumber mosaic virus (CMV) from pepper or tomato, but not to a CMV strain from common bean. Of these eight CMV strains, only the strain from common bean systemically infected common bean cv. Othello. Additional evidence that RT4-4 is a CMV R gene came from the detection of resistance response markers in CMV-challenged leaves of RT4-4 transgenic plants, and the identification of the CMV 2a gene product as the elicitor of the necrosis response. These findings indicate that RT4-4 functions across two plant families and is up-regulated in a non-virus-specific manner. This experimental approach holds promise for providing insights into the mechanisms by which plants activate resistance responses against pathogens.

Source: http://www.pnas.org/cgi/content/abstract/103/32/11856?etoc